Y. Pocker, E. Green
Sep 1, 1976
Citations
0
Influential Citations
12
Citations
Journal
Journal of the American Chemical Society
Abstract
Polarimetric and spectrophotometric methods have been used to study the aminolysis of tri-O-methyl-2-deoxyglucono-delta-lactone over a wide pH and buffer concentration range at 25.0/sup 0/C. A kinetic expression is given to describe the reaction throughout the entire pH and amine nucleophile concentration range. The high reactivity towards aminolysis, the lack of change in the rate-determining step over the entire experimental pH range, and the first-order nucleophilic Bronsted slope of 0.85 place the aminolysis reactions of this delta-lactone within the family of the moderately reactive trifluoroethyl and phenyl acetates. The amines used in the present study (hydroxylamine, glycine ethyl ester, hydrazine, glycinamide, morpholine, 2-methoxyethylamine, ammonia, and glycine) exhibit one or more terms in free-amine concentration (N/sub f/). The term for the hydroxide ion catalyzed hydroxylaminolysis is k/sub 3/(N/sub f//sup 2/a/sub OH/-, with a solvent deuterium isotope effect (k/sub 3//sup H//k/sub 3//sup D/) of 0.6 +- 0.1. The higher-order term k(N/sub f/)/sup 2/a/sub OH/- cannot be detected in this reaction. With morpholine the uncatalyzed first-order term in (N/sub f/), k/sub 1/, arises from a general-base-catalyzed hydrolysis as shown by product analysis and an isotope effect of 1.9 +- 0.2. The overall results indicate that the ring structure in delta-lactones mimics the effect ofmore » the better leaving alkoxy group in open chain esters. These observations are discussed in terms of previously proposed mechanisms for ester aminolysis.« less